More than a third of the world's population is infected with worms (helminths). There are many different types, but the most common are soil-transmitted helminths (roundworm, whipworm and hookworm), schistosomiasis, which can negatively affect children’s health, nutrition and education, and lymphatic filariasis, which is a major cause of acute and chronic morbidity.

Periodic deworming helps avoid the worst effects of infection, leading an increasing list of countries to develop and implement national school deworming and mass drug administration programmes. Implementation of these programmes must be guided by reliable, up-to-date maps of worm distributions. Although thousands of surveys have been done, such maps have generally not been widely available to policy-makers and the managers of control programmes until now.